Who here has a DLP projector (7205) with white lines? - AVS Forum
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post #1 of 9 Old 02-21-2013, 04:37 PM - Thread Starter
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Well, if any of you here have a DLP projector (mine is a InFocus 7205) that is experiencing white vertical lines and/or black horizontal lines... I HAVE A FIX!

Simply, the problem is the connection between the DMD board and the DLP light processor. I took mine apart, cleaned contacts and even replaced the DLP chip trying to correct the problem with no success. But, I did realize that the black bars had become one after one of the times I took it apart and the pattern of white lines had slightly changed and a few were blinking in and out. It had to be a connection problem, not a chip or component failure. After pulling the light engine for the 5th time, I looked at the DMD slot board that the DLP chip is attached to, and noticed the problem, plain as day, right there in my face. Think Xbox 360 problem here, and you start to realize where I'm going with this. The heat sink is attached on 4 corners and uses 4 springs on this model projector to hold down a clamp that sandwiches the PCB of the DMD, the "spring tooth" connection interface, DLP chip and finally the light engine housing. By applying the force on the 4 corners, and not anywhere in the middle, and high heat of a unit like this caused the PCB of the DMD to warp. The clamp, 1/4" think cast aluminium warped as well, so it doesn't hold the entire unit tight in the middle. The teeth on the "spring tooth" component are so minuscule that even a mm would cause them to lose contact.

So, to fix the problem, I used some layers of heat-sink foam (scavenged it from a Plasma TV that I have torn apart that needs to many parts to fix) between the heat-sink and the 1/4" aluminium clamp. And, fixed! It doesn't fully rid the PCB of its warping but it clamps the chip tight enough that it solves the problem. If I had a CNC mill I would mill out a new clamp out of high grade solid aluminium to fix it in a more professional way, but oh well.

If any of you have these projectors laying around and dont want to fix them, I'll take them smile.gif if you want to fix them, go for it and feel free to ask more questions. I'll attach pictures of what I have done below.







sorry, forgot to take a file picture of it re-assembled.

Matt
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post #2 of 9 Old 02-24-2013, 09:03 PM - Thread Starter
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Btw, what would an older projector like this be worth?
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post #3 of 9 Old 04-06-2014, 07:54 PM
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Alphacowboy has correctly diagnosed the cause of the vertical lines on the Infocus 7205.
The aluminum clamp that holds the circuit board against the DLP chip connectors is warping from age or heat. I measured mine to have warped about 0.015". This is enough for connections to be lost and vertical lines to appear. I had 2 projectors with the same problem.


I did not have any material similar to what Alphacowboy used and was concerned that the method may take pressure off the DLP chip heat sink.
My solution to the problem is to straighten the clamp and add custom springs to apply additional pressure to the clamp. The springs do not apply any pressure to the heat sink.

STRAIGHTENING THE CLAMP:
I have an old PanaVise IDE cable press I used for this. This must be done very slowly and carefully. Photos below. I disassembled a feeler and used individual feeler gauges to support the ends of the clamp while I applied pressure in the middle. I started with 0.010" gauges on each end and gently applied pressure to the middle. I then would add another 0.010" on each end and repeat the process. After getting to 0.040" the clamp had a very slight reverse bow to it. At that point I did not go any farther. The clamp is made from a casting so this must be done very slowing and carefully and without a lot of force.



MAKING THE SPRINGS:
I bought a large stainless steel hose clamp from Home Depot that I used to make the springs. I cut out the plain section of hose clamp, the part with no threads. After taking measurements with dial calipers I marked and center punched the center hose clamp at exactly 2.000" intervals. I used a drill press and a small drill to make pilot holes then enlarged each hole to 9/32" with a step drill. Then cut at the center of each hole to make the individual springs. I worked the springs around a piece of pipe until the center of the spring was about a 1/4” tall. Photo below shows the installed springs.







These were great projectors in their day and are still very good today. They are very bright projectors looked excellent when I tested them. I replaced mine long ago due to the vertical lines. I will be selling them on EBay so someone else who can enjoy them. Photo below is of picture from repaired projector.
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post #4 of 9 Old 04-13-2014, 11:00 PM
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Are you selling your SP7205?  If so what do you want for it?

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post #5 of 9 Old 04-15-2014, 05:28 AM
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Yes they are for sale, sent you a PM.
Thanks
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post #6 of 9 Old 06-08-2014, 02:27 PM
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Hi everyone...and special hello to alphaboy and John P.

I used to be the happy owner of an Infocus 7205...but like you i have the vertical lines issue...Thanks to alphaboy, i fixed it but it has lasted long enough for one movie only unfortunaltey. I've tried to improve what i did, but it doesn't work...

John : here's a question for you if you read this. I think i need to go your way or something similar. I was thinking about having the clamp machined in a place where they do such things for car engines...I'm not certain how to say it in english...I think the clamp would loose a little bit of its thickness...Assuming it could be done, is the thickness an issue ?

Sorry for my English
Regards

Tom
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post #7 of 9 Old 06-09-2014, 08:35 AM
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tomti21,

I think the clamp would be very difficult to duplicate. As I recall the underside of the clamp is hollowed out and has a thin plastic insulator. If do not want to attempt straightening the clamp you might want to try just installing the springs. The hose clamp material is not spring steel. Stronger springs could be made by using automotive feeler gauges as a source material, they are spring steel, .020" should work. Also be sure you clean the connection points on the back side of the circuit board.

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post #8 of 9 Old 06-09-2014, 01:01 PM
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Hi John

thanks for your reply...If by staightening you mean to remove the warping from the original clamp, that's exactly what i want to do...But not the same way as you i think. I was talking about a machine that's been designed to fix some car engine main parts...If i had to explain, it would be as if the clamp's surface was fixed with sandpaper to remove the warping...Sorry, when it comes to technical vocabulary, i'm struggling...but maybe you understand what i mean.

I will study your suggestion with springs...and look at the photos.

One last question...I met someone today who knows people at Toshiba (the infocus has also been sold as a Toshiba MT800 as you probably know). If i could get a brand new clamp, would it be enough according to you ? Or the spring trick might be mandatory due to PCB warping too ?

Until now i was doing alphacowboy's trick...it worked a bit but then i tried to combine it with a small wedge to "push" the pcb which is warped too...but still not sufficient...


Thanks again for your support and patience for my average English.
Regards
Tom
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post #9 of 9 Old 06-12-2014, 10:48 PM
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tomti21,


The clamp has 4 alignment pins on the bottom that would prevent resurfacing. Also there is a thin insulator on the bottom and I am not sure if it could be removed and replaced.


I had a MT800 and except for the white case it is identical to the 7205. I have disassembled and modified both the 7205 and MT800. If you can get a new clamp for the MT800 I would recommend it. Also get the circuit board if available. I would also install the springs.


FYI, Toshiba never upgraded the firmware on the MT800, I upgraded mine with the last 7205 firmware.


John




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